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20140926-1 选题
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ChromeOS vs Linux: The Good, the Bad and the Ugly
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================================================================================
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> In the battle between ChromeOS and Linux, both desktop environments have strengths and weaknesses.
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Anyone who believes Google isn't "making a play" for desktop users isn't paying attention. In recent years, I've seen [ChromeOS][1] making quite a splash on the [Google Chromebook][2]. Exploding with popularity on sites such as Amazon.com, it looks as if ChromeOS could be unstoppable.
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In this article, I'm going to look at ChromeOS as a concept to market, how it's affecting Linux adoption and whether or not it's a good/bad thing for the Linux community as a whole. Plus, I'll talk about the biggest issue of all and how no one is doing anything about it.
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### ChromeOS isn't really Linux ###
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When folks ask me if ChromeOS is a Linux distribution, I usually reply that ChromeOS is to Linux what OS X is to BSD. In other words, I consider ChromeOS to be a forked operating system that uses the Linux kernel under the hood. Much of the operating system is made up of Google's own proprietary blend of code and software.
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So while the ChromeOS is using the Linux kernel under its hood, it's still very different from what we might find with today's modern Linux distributions.
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Where ChromeOS's difference becomes most apparent, however, is in the apps it offers the end user: Web applications. With everything being launched from a browser window, Linux users might find using ChromeOS to be a bit vanilla. But for non-Linux users, the experience is not all that different than what they may have used on their old PCs.
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For example: Anyone who is living a Google-centric lifestyle on Windows will feel right at home on ChromeOS. Odds are this individual is already relying on the Chrome browser, Google Drive and Gmail. By extension, moving over to ChromeOS feels fairly natural for these folks, as they're simply using the browser they're already used to.
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Linux enthusiasts, however, tend to feel constrained almost immediately. Software choices feel limited and boxed in, plus games and VoIP are totally out of the question. Sorry, but [GooglePlus Hangouts][3] isn't a replacement for [VoIP][4] software. Not even by a long shot.
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### ChromeOS or Linux on the desktop ###
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Anyone making the claim that ChromeOS hurts Linux adoption on the desktop needs to come up for air and meet non-technical users sometime.
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Yes, desktop Linux is absolutely fine for most casual computer users. However it helps to have someone to install the OS and offer "maintenance" services like we see in the Windows and OS X camps. Sadly Linux lacks this here in the States, which is where I see ChromeOS coming into play.
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I've found the Linux desktop is best suited for environments where on-site tech support can manage things on the down-low. Examples include: Homes where advanced users can drop by and handle updates, governments and schools with IT departments. These are environments where Linux on the desktop is set up to be used by users of any skill level or background.
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By contrast, ChromeOS is built to be completely maintenance free, thus not requiring any third part assistance short of turning it on and allowing updates to do the magic behind the scenes. This is partly made possible due to the ChromeOS being designed for specific hardware builds, in a similar spirit to how Apple develops their own computers. Because Google has a pulse on the hardware ChromeOS is bundled with, it allows for a generally error free experience. And for some individuals, this is fantastic!
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Comically, the folks who exclaim that there's a problem here are not even remotely the target market for ChromeOS. In short, these are passionate Linux enthusiasts looking for something to gripe about. My advice? Stop inventing problems where none exist.
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The point is: the market share for ChromeOS and Linux on the desktop are not even remotely the same. This could change in the future, but at this time, these two groups are largely separate.
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### ChromeOS use is growing ###
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No matter what your view of ChromeOS happens to be, the fact remains that its adoption is growing. New computers built for ChromeOS are being released all the time. One of the most recent ChromeOS computer releases is from Dell. Appropriately named the [Dell Chromebox][5], this desktop ChromeOS appliance is yet another shot at traditional computing. It has zero software DVDs, no anti-malware software, and offfers completely seamless updates behind the scenes. For casual users, Chromeboxes and Chromebooks are becoming a viable option for those who do most of their work from within a web browser.
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Despite this growth, ChromeOS appliances face one huge downside – storage. Bound by limited hard drive size and a heavy reliance on cloud storage, ChromeOS isn't going to cut it for anyone who uses their computers outside of basic web browser functionality.
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### ChromeOS and Linux crossing streams ###
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Previously, I mentioned that ChromeOS and Linux on the desktop are in two completely separate markets. The reason why this is the case stems from the fact that the Linux community has done a horrid job at promoting Linux on the desktop offline.
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Yes, there are occasional events where casual folks might discover this "Linux thing" for the first time. But there isn't a single entity to then follow up with these folks, making sure they’re getting their questions answered and that they're getting the most out of Linux.
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In reality, the likely offline discovery breakdown goes something like this:
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- Casual user finds out Linux from their local Linux event.
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- They bring the DVD/USB device home and attempt to install the OS.
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- While some folks very well may have success with the install process, I've been contacted by a number of folks with the opposite experience.
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- Frustrated, these folks are then expected to "search" online forums for help. Difficult to do on a primary computer experiencing network or video issues.
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- Completely fed up, some of the above frustrated bring their computers back into a Windows shop for "repair." In addition to Windows being re-installed, they also receive an earful about how "Linux isn't for them" and should be avoided.
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Some of you might charge that the above example is exaggerated. I would respond with this: It's happened to people I know personally and it happens often. Wake up Linux community, our adoption model is broken and tired.
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### Great platforms, horrible marketing and closing thoughts ###
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If there is one thing that I feel ChromeOS and Linux on the desktop have in common...besides the Linux kernel, it's that they both happen to be great products with rotten marketing. The advantage however, goes to Google with this one, due to their ability to spend big money online and reserve shelf space at big box stores.
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Google believes that because they have the "online advantage" that offline efforts aren't really that important. This is incredibly short-sighted and reflects one of Google's biggest missteps. The belief that if you're not exposed to their online efforts, you're not worth bothering with, is only countered by local shelf-space at select big box stores.
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My suggestion is this – offer Linux on the desktop to the ChromeOS market through offline efforts. This means Linux User Groups need to start raising funds to be present at county fairs, mall kiosks during the holiday season and teaching free classes at community centers. This will immediately put Linux on the desktop in front of the same audience that might otherwise end up with a ChromeOS powered appliance.
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If local offline efforts like this don't happen, not to worry. Linux on the desktop will continue to grow as will the ChromeOS market. Sadly though, it will absolutely keep the two markets separate as they are now.
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--------------------------------------------------------------------------------
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via: http://www.datamation.com/open-source/chromeos-vs-linux-the-good-the-bad-and-the-ugly-1.html
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作者：[Matt Hartley][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://www.datamation.com/author/Matt-Hartley-3080.html
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[1]:http://en.wikipedia.org/wiki/Chrome_OS
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[2]:http://www.google.com/chrome/devices/features/
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[3]:https://plus.google.com/hangouts
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[4]:http://en.wikipedia.org/wiki/Voice_over_IP
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[5]:http://www.pcworld.com/article/2602845/dell-brings-googles-chrome-os-to-desktops.html
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How To Reset Root Password On CentOS 7
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================================================================================
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The way to reset the root password on centos7 is totally different to Centos 6. Let me show you how to reset root password in CentOS 7.
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1 – In the boot grub menu select option to edit.
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2 – Select Option to edit (e).
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3 – Go to the line of Linux 16 and change ro with rw init=/sysroot/bin/sh.
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4 – Now press Control+x to start on single user mode.
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5 – Now access the system with this command.
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chroot /sysroot
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6 – Reset the password.
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passwd root
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7 – Update selinux information
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touch /.autorelabel
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8 – Exit chroot
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exit
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9 – Reboot your system
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reboot
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That’s it. Enjoy.
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--------------------------------------------------------------------------------
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via: http://www.unixmen.com/reset-root-password-centos-7/
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作者：M.el Khamlichi
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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How to manage configurations in Linux with Puppet and Augeas
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================================================================================
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Although [Puppet][1](注：此文原文原文中曾今做过，文件名：“20140808 How to install Puppet server and client on CentOS and RHEL.md”,如果翻译发布过，可修改此链接为发布地址) is a really unique and useful tool, there are situations where you could use a bit of a different approach. Situations like modification of configuration files which are already present on several of your servers and are unique on each one of them at the same time. Folks from Puppet labs realized this as well, and integrated a great tool called [Augeas][2] that is designed exactly for this usage.
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Augeas can be best thought of as filling for the gaps in Puppet's capabilities where an objectspecific resource type (such as the host resource to manipulate /etc/hosts entries) is not yet available. In this howto, you will learn how to use Augeas to ease your configuration file management.
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### What is Augeas? ###
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Augeas is basically a configuration editing tool. It parses configuration files in their native formats and transforms them into a tree. Configuration changes are made by manipulating this tree and saving it back into native config files.
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### What are we going to achieve in this tutorial? ###
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We will install and configure the Augeas tool for use with our previously built Puppet server. We will create and test several different configurations with this tool, and learn how to properly use it to manage our system configurations.
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### Prerequisites ###
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We will need a working Puppet server and client setup. If you don't have it, please follow my previous tutorial.
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Augeas package can be found in our standard CentOS/RHEL repositories. Unfortunately, Puppet uses Augeas ruby wrapper which is only available in the puppetlabs repository (or [EPEL][4]). If you don't have this repository in your system already, add it using following command:
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On CentOS/RHEL 6.5:
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# rpm -ivh https://yum.puppetlabs.com/el/6.5/products/x86_64/puppetlabsrelease610.noarch.rpm
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On CentOS/RHEL 7:
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# rpm -ivh https://yum.puppetlabs.com/el/7/products/x86_64/puppetlabsrelease710.noarch.rpm
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After you have successfully added this repository, install RubyAugeas in your system:
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# yum install rubyaugeas
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Or if you are continuing from my last tutorial, install this package using the Puppet way. Modify your custom_utils class inside of your /etc/puppet/manifests/site.pp to contain "rubyaugeas" inside of the packages array:
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class custom_utils {
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package { ["nmap","telnet","vimenhanced","traceroute","rubyaugeas"]:
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ensure => latest,
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allow_virtual => false,
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}
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}
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### Augeas without Puppet ###
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As it was said in the beginning, Augeas is not originally from Puppet Labs, which means we can still use it even without Puppet itself. This approach can be useful for verifying your modifications and ideas before applying them in your Puppet environment. To make this possible, you need to install one additional package in your system. To do so, please execute following command:
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# yum install augeas
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### Puppet Augeas Examples ###
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For demonstration, here are a few example Augeas use cases.
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#### Management of /etc/sudoers file ####
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1. Add sudo rights to wheel group
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This example will show you how to add simple sudo rights for group %wheel in your GNU/Linux system.
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# Install sudo package
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package { 'sudo':
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ensure => installed, # ensure sudo package installed
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}
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# Allow users belonging to wheel group to use sudo
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augeas { 'sudo_wheel':
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context => '/files/etc/sudoers', # The target file is /etc/sudoers
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changes => [
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# allow wheel users to use sudo
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'set spec[user = "%wheel"]/user %wheel',
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'set spec[user = "%wheel"]/host_group/host ALL',
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'set spec[user = "%wheel"]/host_group/command ALL',
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'set spec[user = "%wheel"]/host_group/command/runas_user ALL',
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]
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}
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Now let's explain what the code does: **spec** defines the user section in /etc/sudoers, **[user]** defines given user from the array, and all definitions behind slash ( / ) are subparts of this user. So in typical configuration this would be represented as:
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user host_group/host host_group/command host_group/command/runas_user
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Which is translated into this line of /etc/sudoers:
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%wheel ALL = (ALL) ALL
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2. Add command alias
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The following part will show you how to define command alias which you can use inside your sudoers file.
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# Create new alias SERVICES which contains some basic privileged commands
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augeas { 'sudo_cmdalias':
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context => '/files/etc/sudoers', # The target file is /etc/sudoers
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changes => [
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"set Cmnd_Alias[alias/name = 'SERVICES']/alias/name SERVICES",
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"set Cmnd_Alias[alias/name = 'SERVICES']/alias/command[1] /sbin/service",
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"set Cmnd_Alias[alias/name = 'SERVICES']/alias/command[2] /sbin/chkconfig",
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"set Cmnd_Alias[alias/name = 'SERVICES']/alias/command[3] /bin/hostname",
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"set Cmnd_Alias[alias/name = 'SERVICES']/alias/command[4] /sbin/shutdown",
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]
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}
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Syntax of sudo command aliases is pretty simple: **Cmnd_Alias** defines the section of command aliases, **[alias/name]** binds all to given alias name, /alias/name **SERVICES** defines the actual alias name and alias/command is the array of all the commands that should be part of this alias. The output of this command will be following:
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Cmnd_Alias SERVICES = /sbin/service , /sbin/chkconfig , /bin/hostname , /sbin/shutdown
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For more information about /etc/sudoers, visit the [official documentation][5].
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#### Adding users to a group ####
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To add users to groups using Augeas, you might want to add the new user either after the gid field or after the last user. We'll use group SVN for the sake of this example. This can be achieved by using the following command:
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In Puppet:
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augeas { 'augeas_mod_group:
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context => '/files/etc/group', # The target file is /etc/group
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changes => [
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"ins user after svn/*[self::gid or self::user][last()]",
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"set svn/user[last()] john",
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]
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}
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Using augtool:
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augtool> ins user after /files/etc/group/svn/*[self::gid or self::user][last()] augtool> set /files/etc/group/svn/user[last()] john
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### Summary ###
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By now, you should have a good idea on how to use Augeas in your Puppet projects. Feel free to experiment with it and definitely go through the official Augeas documentation. It will help you get the idea how to use Augeas properly in your own projects, and it will show you how much time you can actually save by using it.
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If you have any questions feel free to post them in the comments and I will do my best to answer them and advise you.
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### Useful Links ###
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- [http://www.watzmann.net/categories/augeas.html][6]: contains a lot of tutorials focused on Augeas usage.
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- [http://projects.puppetlabs.com/projects/1/wiki/puppet_augeas][7]: Puppet wiki with a lot of practical examples.
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--------------------------------------------------------------------------------
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via: http://xmodulo.com/2014/09/manage-configurations-linux-puppet-augeas.html
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作者：[Jaroslav Štěpánek][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://xmodulo.com/author/jaroslav
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[1]:http://xmodulo.com/2014/08/install-puppet-server-client-centos-rhel.html
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[2]:http://augeas.net/
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[3]:http://xmodulo.com/manage-configurations-linux-puppet-augeas.html
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[4]:http://xmodulo.com/2013/03/how-to-set-up-epel-repository-on-centos.html
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[5]:http://augeas.net/docs/references/lenses/files/sudoers-aug.html
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[6]:http://www.watzmann.net/categories/augeas.html
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[7]:http://projects.puppetlabs.com/projects/1/wiki/puppet_augeas
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How to monitor user login history on CentOS with utmpdump
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================================================================================
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Keeping, maintaining and analyzing logs (i.e., accounts of events that have happened during a certain period of time or are currently happening) are among the most basic and essential tasks of a Linux system administrator. In case of user management, examining user logon and logout logs (both failed and successful) can alert us about any potential security breaches or unauthorized use of our system. For example, remote logins from unknown IP addresses or accounts being used outside working hours or during vacation leave should raise a red flag.
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On a CentOS system, user login history is stored in the following binary files:
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- /var/run/utmp (which logs currently open sessions) is used by who and w tools to show who is currently logged on and what they are doing, and also by uptime to display system up time.
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- /var/log/wtmp (which stores the history of connections to the system) is used by last tool to show the listing of last logged-in users.
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- /var/log/btmp (which logs failed login attempts) is used by lastb utility to show the listing of last failed login attempts. `
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In this post I'll show you how to use utmpdump, a simple program from the sysvinit-tools package that can be used to dump these binary log files in text format for inspection. This tool is available by default on stock CentOS 6 and 7. The information gleaned from utmpdump is more comprehensive than the output of the tools mentioned earlier, and that's what makes it a nice utility for the job. Besides, utmpdump can be used to modify utmp or wtmp, which can be useful if you want to fix any corrupted entries in the binary logs.
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### How to Use Utmpdump and Interpret its Output ###
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As we mentioned earlier, these log files, as opposed to other logs most of us are familiar with (e.g., /var/log/messages, /var/log/cron, /var/log/maillog), are saved in binary file format, and thus we cannot use pagers such as less or more to view their contents. That is where utmpdump saves the day.
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In order to display the contents of /var/run/utmp, run the following command:
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# utmpdump /var/run/utmp
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To do the same with /var/log/wtmp:
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# utmpdump /var/log/wtmp
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and finally with /var/log/btmp:
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# utmpdump /var/log/btmp
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As you can see, the output formats of three cases are identical, except for the fact that the records in the utmp and btmp are arranged chronologically, while in the wtmp, the order is reversed.
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Each log line is formatted in multiple columns described as follows. The first field shows a session identifier, while the second holds PID. The third field can hold one of the following values: ~~ (indicating a runlevel change or a system reboot), bw (meaning a bootwait process), a digit (indicates a TTY number), or a character and a digit (meaning a pseudo-terminal). The fourth field can be either empty or hold the user name, reboot, or runlevel. The fifth field holds the main TTY or PTY (pseudo-terminal), if that information is available. The sixth field holds the name of the remote host (if the login is performed from the local host, this field is blank, except for run-level messages, which will return the kernel version). The seventh field holds the IP address of the remote system (if the login is performed from the local host, this field will show 0.0.0.0). If DNS resolution is not provided, the sixth and seventh fields will show identical information (the IP address of the remote system). The last (eighth) field indicates the date and time when the record was created.
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### Usage Examples of Utmpdump ###
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Here are a few simple use cases of utmpdump.
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1. Check how many times (and at what times) a particular user (e.g., gacanepa) logged on to the system between August 18 and September 17.
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# utmpdump /var/log/wtmp | grep gacanepa
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If you need to review login information from prior dates, you can check the wtmp-YYYYMMDD (or wtmp.[1...N]) and btmp-YYYYMMDD (or btmp.[1...N]) files in /var/log, which are the old archives of wtmp and btmp files, generated by [logrotate][1].
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2. Count the number of logins from IP address 192.168.0.101.
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# utmpdump /var/log/wtmp | grep 192.168.0.101
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||||
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||||
|
||||
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||||
3. Display failed login attempts.
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||||
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# utmpdump /var/log/btmp
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||||
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||||
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||||
In the output of /var/log/btmp, every log line corresponds to a failed login attempt (e.g., using incorrect password or a non-existing user ID). Logon using non-existing user IDs are highlighted in the above impage, which can alert you that someone is attempting to break into your system by guessing commonly-used account names. This is particularly serious in the cases when the tty1 was used, since it means that someone had access to a terminal on your machine (time to check who has keys to your datacenter, maybe?).
|
||||
|
||||
4. Display login and logout information per user session.
|
||||
|
||||
# utmpdump /var/log/wtmp
|
||||
|
||||
|
||||
|
||||
In /var/log/wtmp, a new login event is characterized by '7' in the first field, a terminal number (or pseudo-terminal id) in the third field, and username in the fourth. The corresponding logout event will be represented by '8' in the first field, the same PID as the login in the second field, and a blank terminal number field. For example, take a close look at PID 1463 in the above image.
|
||||
|
||||
- On [Fri Sep 19 11:57:40 2014 ART] the login prompt appeared in tty1.
|
||||
- On [Fri Sep 19 12:04:21 2014 ART], user root logged on.
|
||||
- On [Fri Sep 19 12:07:24 2014 ART], root logged out.
|
||||
|
||||
On a side note, the word LOGIN in the fourth field means that a login prompt is present in the terminal specified in the fifth field.
|
||||
|
||||
So far I covered somewhat trivial examples. You can combine utmpdump with other text sculpting tools such as awk, sed, grep or cut to produce filtered and enhanced output.
|
||||
|
||||
For example, you can use the following command to list all login events of a particular user (e.g., gacanepa) and send the output to a .csv file that can be viewed with a pager or a workbook application, such as LibreOffice's Calc or Microsoft Excel. Let's display PID, username, IP address and timestamp only:
|
||||
|
||||
# utmpdump /var/log/wtmp | grep -E "\[7].*gacanepa" | awk -v OFS="," 'BEGIN {FS="] "}; {print $2,$4,$7,$8}' | sed -e 's/\[//g' -e 's/\]//g'
|
||||
|
||||
|
||||
|
||||
As represented with three blocks in the image, the filtering logic is composed of three pipelined steps. The first step is used to look for login events ([7]) triggered by user gacanepa. The second and third steps are used to select desired fields, remove square brackets in the output of utmpdump, and set the output field separator to a comma.
|
||||
|
||||
Of course, you need to redirect the output of the above command to a file if you want to open it later (append "> [name_of_file].csv" to the command).
|
||||
|
||||
|
||||
|
||||
In more complex examples, if you want to know what users (as listed in /etc/passwd) have not logged on during the period of time, you could extract user names from /etc/passwd, and then run grep the utmpdump output of /var/log/wtmp against user list. As you see, possibility is limitless.
|
||||
|
||||
Before concluding, let's briefly show yet another use case of utmpdump: modify utmp or wtmp. As these are binary log files, you cannot edit them as is. Instead, you can export their content to text format, modify the text output, and then import the modified content back to the binary logs. That is:
|
||||
|
||||
# utmpdump /var/log/utmp > tmp_output
|
||||
<modify tmp_output using a text editor>
|
||||
# utmpdump -r tmp_output > /var/log/utmp
|
||||
|
||||
This can be useful when you want to remove or fix any bogus entry in the binary logs.
|
||||
|
||||
To sum up, utmpdump complements standard utilities such as who, w, uptime, last, lastb by dumping detailed login events stored in utmp, wtmp and btmp log files, as well as in their rotated old archives, and that certainly makes it a great utility.
|
||||
|
||||
Feel free to enhance this post with your comments.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://xmodulo.com/2014/09/monitor-user-login-history-centos-utmpdump.html
|
||||
|
||||
作者：[Gabriel Cánepa][a]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://xmodulo.com/author/gabriel
|
||||
[1]:http://xmodulo.com/2014/09/logrotate-manage-log-files-linux.html
|
||||
Loading…
Reference in New Issue
Block a user